Polymers and copolymers of, and surgical devices made from lactide and/or glycolide and/or related compounds are well-known. See, e.g., U.S. Pat. Nos. 2,668,162, 2,683,136, 2,703,316, 2,758,987, 3,225,766, 3,268,486, 3,268,487, 3,297,033, 3,422,181, 3,442,871, 3,463,158, 3,468,853, 3,531,561, 3,565,869, 3,597,449, 3,620,218, 3,626,948, 3,636,956, 3,736,646, 3,739,773, 3,772,420, 3,733,919, 3,781,349, 3,784,585, 3,792,010, 3,797,499, 3,839,297, 3,846,382, 3,867,190, 3,987,937,, 3,878,284, 3,896,802, 3,902,497, 3,937,223, 3,982,543 4,033,938, 4,045,418, 4,057,537, 4,060,089, 4,137,921, 4,157,437, 4,243,775, 4,246,904, 4,273,920, 4,275,813, 4,279,249, 4,300,565, and 4,744,365, U.K. Pat. or Appln. Nos. 779,291, 1,332,505, 1,414,600 and 2,102,827, D. K. Gilding et al., "Biodegradable polymers for-use in surgery-polyglycolic/poly (lactic acid) homo-and copolymers: 1, "Polymer, Volume 20, pages 1459-1464 (1979), and D. F. Williams (ed.) Biocompatibility of Clinical Implant Materials, Volume II, chapter 9: "Biodegradable Polymers" (1981).
Surgical devices prepared from copolymers containing dioxanone and polycarbonates are also known in the art. For example, U.S. Pat. No. 4,052,988 describes random copolymers containing dioxanone and up to 50 percent by weight of other copolymerizable monomers which produce non-toxic and absorbable copolymers.
As another example, U.S. Pat. No. 5,037,950 describes copolymers having sequential units of rho-dioxanone and sequential units of either tetramethylene carbonate, pentamethylene carbonate, hexamethylene carbonate, heptamethylene carbonate, octamethylene carbonate, nonamethylene carbonate, decamethylene carbonate, undecamethylene carbonate, and dodecamethylene carbonate, with hexamethylene carbonate being preferred. The '950 patent describes neither random copolymers nor copolymers containing trimethylene carbonate.
As yet a further example, U.S. Pat. No. 5,145,945 generically describes random copolymers of trimethylene carbonate and dioxanones other than carbonates. In addition, see U.S. Pat. Nos. 4,891,263; 4,916,193; 4,902,203; and 5,152,781.
As described above bioabsorbable sutures are known in the art. However, in the manufacture of sutures an important characteristic of a suture is the amount of effort typically required to straighten the suture upon its removal from the package in order to ready the suture for use. This effort appears to be related to the "strain energy" of the suture, i.e., the integration of the stress-strain curve for the suture measured in kilogram-mm, and is equivalent to the work expended in elongating the monofilament by a specified percentage of its original length. As the strain energy of a given size of suture decreases so, too, does the amount of effort required to straighten the suture prior to use. A decrease in strain energy also appears to relate to the perceived flexibility of the suture.
Therefore, it would be advantageous to provide a bioabsorbable suture which exhibits a desired absorption profile and improved flexibility and handling characteristics when compared to commercially available sutures having the same absorption profile, while maintaining other desired properties, such as knot-pull strength and straight-pull retention.